At 10:08 AM 2/20/98 -0500, you wrote:
> Engines NEED a
> certain amount of backpressure to operate efficiently.
I would agree here, although I would offer that the difference in
backpressure between a 2.5 and 3" pipe after the cat would not be as much a
factor in reducing backpressure as the changing of a muffler or adding headers.
THe further through the exhaust system you go, the less effect backpressure
has on the engine.
> My point: if you are NOT installing headers, new y pipe AND hi flow
> cat in a TRUE dual exhaust setup you dont gain much and may even lose
> due to turbulance and resonance.
The whole point of headers is to smooth and un-restrict the flow of exhaust
gases from the chamber. In fact, the whole idea of ANY exhaust mod is to get
the spent gases out of the chamber more efficiently and more completely in
order to clear space for the incoming air/fuel charge. Headers do this by
helping to sweep out the spent gases.
LEss backpressure will also aid in this mission.
I have heard before that some feel that certain engines actually NEED a
certain amount of backpressure to run well.
I guess this could be true. But I can only speak from my experience. My 3"
system is a BIG improvement over stock...
> You are absolutely correct in stating that aftermarket or custom
> mandrel bent pipes are better than stock. Joe
> An indication of "over exhaust conditions" is a very noticable "bap,
> bap bap bap" sound during decelleration. Ever have a muffler fall off
> a Vega??
Well, if this is the case, then how about stock cars, etc?? I know its a
different animal, but there exhausts are MIGHTY loud and "bappy"...
They tune these engines to produce WAY BIGGER HP than we can ever hope for
out of our stockers.
I think that the "bap bap bap" IS indeed a diruption of the sound waves
created by the exhaust pulse......Whether this would create a lessening of
HP I would say not. I mean, with this thinking, my stock 85 reliant's
muffler is super quiet but the HP sucks.....I have heard Cars with monster
duals wit hTurbo mufflers that were quiet as hell but still kicked ass. So
I cannot correlate the "sound" of an exhaust with the "powe" produced. This
would be a case-by-case kind of thing, I think.
>
>
>______________________________ Reply Separator
_________________________________
>Subject: Re: DML: Gibson exhaust installation
>Author: <dakota-truck@buffnet.net> at internet
>Date: 2/20/98 9:16 AM
>
>
>Joe,
>
>I also have to disagree with the info you got from Flowmaster. The stock
>2.5" exhaust may be "adequate", but it still presents more ristriction
>on the exhaust than an aftermarket single 3" or dual 2.5". Exhaust
>restriction is a cumulative effect due to the fluid resistance between
>exhaust gases and the sides of the pipes and any obstructions. The
>resistance values for all exhaust components are added together to
>calculate a flow rate for the system. In other words, even with a 2.5"
>openning through the cat, you will have a higher flow rate with a 3" cat
>back than a 2.5" cat back.
>
>There is a point of diminishing returns, however. I agree that the duals
>don't do much for you from a performance increase standpoint vs. a 3"
>single, unless you have other mods to take advantage of them.
>
>My biggest objection to leaving the stock exit pipe (muffler back) is
>2.5" with crimped bends. The crimped bends produce increased exhaust gas
>turbulence and flow resistance. The aftermarket pipes (even custom bent
>jobs from the local muffler shop) are mandrel bent, which provide a nice
>smooth curve and less restriction.
>
>jeff
>98 RC 4x2 V8 5spd 3.55SG flares
>
>
>Klaus Wilkens wrote:
>>
>> Joe,
>>
>> Flowmaster is trying to sell Flowmaster. What youwere told doesn't
compute. If
>the Y
>> pipe and Cat are the major restriction opening up the exhaust system
after the
>cat
>> would have negligible effect.
>>
>> I have a 94 Sport with the 5.2, 5spd, and 3.90 gears. I've had the truck
since
>new
>> and have had it to the track a few times. The most marked single improvement
>was the
>> Gibson cat back exhaust with a set of JBA shorty headers which use the
factory
>Y
>> pipe. I picked up 2 mph at the strip and 2 mpg on the road with this
>modification.
>>
>> A few years ago CC did a 2.2 turbo package called the Super 60. The
>development was
>> done on a dyno and with mufflers and the Dynomax Ultra made 20HP more
than the
>> Flowmaster.
>>
>> KW
>>
>> Joe Borg wrote:
>>
>> > Jeff, I recently called flowmaster. They stated with minor mods, the
>> > stock exhaust system is more than adequate when a flowmaster 2
chamber
>> > muffler is installed. They stated 3" pipe does not have enough
>> > backpressure and although sounding "meaner" woulsd actually slow you
>> > down. The concept of single in dual out mufflers is pure show and no
>> > go. An exhaust system can only be as efficient as its weakest point -
>> > the 2 into 1 y pipe and cat. Unless you install 2 cats with a true
>> > dual setup you are gaining nothing but sound and appearance. Joe Borg
>> >
>
>jeff
>98 RC 4x2 V8 5spd 3.55SG flares
>
>
>
>
>
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